1. Field of the Disclosure
The present disclosure relates to a light emitting diode (LED) device, and more particularly, to an LED device which employs a large spatial separation between a luminescence-generating semiconductor and a phosphorescence-generating light-conversion material and has a reflector cup having a diffuse reflective surface to diffusely reflect light, thus improving a luminous efficiency.
2. Description of the Related Art
Light emitting diode (LED) devices convert ultraviolet light rays or blue light rays emitted from an LED chip into visible light rays that have a longer wavelength. Recently, the LED device is drawing wide attention for its function of emitting white light or visible light rays of various colors. For example, in a white LED device, an ultraviolet ray emitted from the LED chip excites a phosphor. Then, the three primary colors of light, that is, red (R), green (G), and blue (B) visible rays, or yellow (Y) or blue (B) visible rays are emitted from the phosphor. The visible color rays emitted from the phosphor vary dependent on the composition of the phosphor. These visible rays combined with each other result in white light to the eyes of a human.
FIG. 1 is a sectional view of a conventional lamp type LED device that is disclosed in U.S. Pat. No. 6,069,440. Referring to FIG. 1, a lamp type LED device 10 includes a mount lead 11 and an inner lead 12. An LED chip 14 is installed in a reflector cup 20 that is formed in the upper portion of the mount lead 11. The LED chip 14 has an n electrode and a p electrode which are electrically connected to the mount lead 11 and the inner lead 12, respectively, by a wire 15. The LED chip 14 is covered by a phosphor layer 16 that is a mixture of phosphor and transparent encapsulant. These constituent elements are surrounded by a seal substance 17. The reflector cup 20 is coated with silver (Ag) or aluminum (Al) for the high reflection of visible light rays.
FIGS. 2A, 2B, and 2C show various arrangements of the phosphor in the reflector cup 20. Referring to FIGS. 2A, 2B, and 2C, the LED chip 14 is arranged at the bottom of the reflector cup 20. Phosphors 22 are distributed in the transparent encapsulant 16 in the reflector cup 20.
FIG. 2A shows the distribution of the phosphors 22 that are resolved in the transparent encapsulant (coating resin or polymer) 16 in the reflector cup 20. The LED chip 14 emits luminescence that excites the phosphors 22 to emit phosphorescence. Part of the phosphorescence collides against the surface of the LED chip 14 where it is reabsorbed. Thus, the luminous efficiency is lowered.
FIG. 2B shows that the phosphors 22 are distributed on the surface of the LED chip 14. in this case, a probability that the phosphorescence of the phosphors 22 collides against the LED chip 14 increases so that the luminous efficiency is reduced.
FIG. 2C shows that the phosphors 22 are separated from the LED chip 14. In this instance, the probability that the phosphorescence directly collides against the LED chip 14 is relatively lowered.